It is well known in the art to use shear couplers between adjacent sucker rods in a sucker rod string that is used to drive a downhole pump in a wellbore for the purpose of producing hydrocarbon fluids to the surface. Conventionally, such couplers feature inner and outer members that mate together in an axial manner placing a portion of the inner member within a hollow interior of the other member, and then one of more shear pins that lock together these members by passing radially through the wall of the outer member into engagement with the inner member.
Other shear couplers have employed a reduced-diameter shear neck between the body and externally threaded head of a pin coupler that is matingly threaded into an internally threaded box coupler, as shown in Canadian Patent No. 1298715, in which the solution is described as being advantageous over shear pin designs in which the pins have been known to prone to premature fatigue.
U.S. Patent Application Publication No. 2009/0271966 discloses another pin coupler with a shear neck that adds an additional means for preventing backing off of the threaded connection between the pin and box couplers by radially expanding the head of the pin coupler by forcing a ball bearing into a counterbore in the head, where slots radiating outwardly from the counterbore allow the head to deform outwardly into tighter engagement with the threads of the surrounding box coupler.
U.S. Patent Application Publication No. 2004/0202521 discloses a box coupler with a similar stress concentration point of reduced diameter at which the string will shear under sufficient axial force, but using external circumferential groove the coupler body to form this weakened intentional-failure point.
U.S. Pat. No. 4,411,546 discloses a sucker rod shear coupler in which a shear neck of the coupler body is surrounded by an outer sleeve that is sealed to the body above and below the shear neck to protect the shear neck from corrosive fluids and prevent deflection of same. The shear coupler is used in a reciprocating, rather than rotating, sucker rod string driven by a walking beam to operate a reciprocating downhole pump. The coupler lacks any means for rotationally locking the sleeve to other components, whereby if used in a rotational sucker rod string to drive a rotary downhole pump, the sleeve would be limited in its ability to effectively transfer torque across the coupler during rotation of the sucker rod string, thereby relying heavily or entirely on the shear neck to provide the torque handling capacity of the coupler.
U.S. Pat. No. 5,470,118 discloses a shear device for use with a well service tool on a sandline. Using end caps threaded onto opposing ends of the shear body, an outer sleeve is once again disposed around the shear body to protect the shear neck and prevent deflection of same. The lower cap and the sleeve are not interlocked, but rather remain in axially-slidable relation to one another, whereby the sleeve would not transfer torque across the coupler in the event that it were applied to a rotationally driven sucker rod string.
U.S. Pat. No. 8,636,057 discloses a shear coupling again having a necked shear body and surrounding outer sleeve, but additionally adds an internally threaded locking member that threads onto an externally threaded male end of the shear body inside the bore of the hollow sleeve in order to maintain the shear body in a state of axial pre-tension to enhance fatigue resistance in reciprocating pump applications or rotary pump applications with wellbore deviations. An end of the outer sleeve and a shouldered area of the shear body against which the end of the sleeve is abutted are matingly profiled with a polygonal cross-section to enable co-rotation of the two components and torque transfer across same for use in rotary pump applications.
U.S. Patent Application Publication 2013/0032326 also discloses a shear coupling featuring a reduced-neck inner shear body and surrounding outer sleeve, which have mating polygonal profiles to enable torque transfer across the coupling.
Applicant has developed unique shear coupler designs that are useful as alternatives and/or improvements to the forgoing prior art.